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. Genetic parameters for Brahman,(BRAH) and Tropical Composite (TCOMP) cattle were estimated for steer production traits recorded at weaning (WEAN), 80 days post-weaning (POSTW), feedlot entry (ENTRY) and after  120 days feedlot finishing (EXIT). The TCOMP was 50% Bos indicus, African Sanga or other tropically adapted Bos taurus,and50%non-tropicallyadaptedBostaurus.Datainvolved2216steers,comprising1007BRAHby53siresand1209 TCOMPby50sires. Individualdailyfeed intake(DFI)andresidual feedintake (RFI)wereassessedon680BRAH and783 TCOMP steers over an ~70-day feedlot test. Other traits were liveweight (LWT), average daily gain (ADG), ultrasonically scanned rump (SP8) fat depth, rib (SRIB) fat depth, M. longissimus area (SEMA) and intra-muscular fat % (SIMF), body condition score (CS), hip height (HH), flight time (FT) and serum insulin-like growth factor-I concentration (IGF-I). BRAH were significantly (P , in TCOMP, suggesting a clear potential to genetically change RFI in both genotypes. Trait variances and genetic correlations often differed between the genotypes, supporting the use of genotype- specific parameters in genetic evaluation. The genotype,differences may,be associated with evolutionary changes that have occurred,in B. indicus as a part of their adaptation to tropical environments. Measures with potential to be used as genetic indicators of DFI were LWT measures in BRAH and TCOMP, ADG at ENTRY in TCOMP, and SP8 and SIMF at ENTRY in BRAH. Measures with potential to be genetic indicators of RFI were HH and ADG at ENTRY in BRAH, and IGF-I in both genotypes. Taller and faster-growing BRAH steers at ENTRY had genetically lower RFI. IGF-I was negatively genetically correlated with RFI whether IGF-I was measured at POSTW, ENTRY or EXIT. SRIB fatness at EXIT was strongly positively genetically correlated with RFI in TCOMP but only lowly correlatedinBRAH.FatnessatENTRYwaslowlyandnegativelygeneticallycorrelatedwithRFI.Theresultsemphasisethe need for a population-specific understanding,of trait relationships and of trait differences between,measurement,times if genetic indicator traits are to be utilised in genetic evaluation of RFI. Additional keywords: adaptation, correlations, genotype · environment, heritability, IGF-I, variance components.

animal production science

Genetics of steer daily and residual feed intake in two tropical beef genotypes, and relationships among intake, body composition, growth and other post-weaning measures